U.S. patent application number 12/334778 was filed with the patent office on 2009-10-01 for reserve torque for lean equivalence ratio requests.
This patent application is currently assigned to GM GLOBAL TECHNOLOGY OPERATIONS, INC.. Invention is credited to Robert J. Genslak, Robert C. Simon, JR., Edward Stuteville, Christopher E. Whitney, Cheryl A. Williams.
Application Number | 20090241899 12/334778 |
Document ID | / |
Family ID | 41115241 |
Filed Date | 2009-10-01 |
United States Patent
Application |
20090241899 |
Kind Code |
A1 |
Whitney; Christopher E. ; et
al. |
October 1, 2009 |
Reserve Torque for Lean Equivalence Ratio Requests
Abstract
A reserve torque system comprises a first module and a reserve
torque module. The first module generates a first signal a
predetermined period before an equivalence ratio (EQR) of an
air/fuel mixture supplied to an engine is transitioned from a
non-lean EQR to a lean EQR. The reserve torque module creates a
reserve torque between when the first signal is generated and when
the EQR is transitioned to the lean EQR.
Inventors: |
Whitney; Christopher E.;
(Highland, MI) ; Genslak; Robert J.; (Macomb,
MI) ; Stuteville; Edward; (Linden, MI) ;
Williams; Cheryl A.; (Howell, MI) ; Simon, JR.;
Robert C.; (Brighton, MI) |
Correspondence
Address: |
Harness Dickey & Pierce, P.L.C.
P.O. Box 828
Bloomfield Hills
MI
48303
US
|
Assignee: |
GM GLOBAL TECHNOLOGY OPERATIONS,
INC.
DETROIT
MI
|
Family ID: |
41115241 |
Appl. No.: |
12/334778 |
Filed: |
December 15, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61039524 |
Mar 26, 2008 |
|
|
|
Current U.S.
Class: |
123/406.45 |
Current CPC
Class: |
F02D 41/0002 20130101;
Y02T 10/40 20130101; F02D 41/1475 20130101; Y02T 10/46 20130101;
F02D 2250/22 20130101; F02D 37/02 20130101; F02P 5/1504 20130101;
F02D 41/10 20130101; Y02T 10/42 20130101 |
Class at
Publication: |
123/406.45 |
International
Class: |
F02D 43/04 20060101
F02D043/04; F02P 5/15 20060101 F02P005/15 |
Claims
1. A reserve torque system comprising: a first module that
generates a first signal a predetermined period before an
equivalence ratio (EQR) of an air/fuel mixture supplied to an
engine is transitioned from a non-lean EQR to a lean EQR; and a
reserve torque module that creates a reserve torque between when
said first signal is generated and when said EQR is transitioned to
said lean EQR.
2. The reserve torque system of claim 1 further comprising an
actuation module that increases at least one engine airflow
parameter and retards spark timing before said EQR is transitioned
to said lean EQR.
3. The reserve torque system of claim 2 wherein said actuation
module maintains said at least one engine airflow parameter until
said EQR is transitioned from said lean EQR to a second non-lean
EQR.
4. The reserve torque system of claim 3 wherein said first module
transitions said EQR from said non-lean EQR to a rich EQR during a
first period and transitions said EQR from said rich EQR to said
lean EQR during a second period that is after said first period,
wherein said non-lean EQR is a stoichiometric EQR, and wherein said
actuation module increases said at least one engine airflow
parameter before said first period and maintains said at least one
engine airflow parameter until said EQR is transitioned from said
lean EQR to said second non-lean EQR.
5. The reserve torque system of claim 4 wherein said actuation
module retards said spark timing when said at least one engine
airflow parameter increases and further retards said spark timing
while said EQR transitions from said non-lean EQR to said rich
EQR.
6. The reserve torque system of claim 1 wherein said first module
generates a second signal based on said lean EQR, and wherein said
reserve torque module creates said reserve torque based on said
second signal.
7. The reserve torque system of claim 1 wherein said first module
transitions said EQR to said lean EQR after said reserve torque is
created.
8. The reserve torque system of claim 1 wherein said first module
transitions said EQR to said lean EQR a predetermined period after
said first signal is generated.
9. The reserve torque system of claim 1 wherein said first module
selectively diagnoses a fault in a catalyst associated with said
engine after said EQR is transitioned to said lean EQR.
10. The reserve torque system of claim 9 wherein said first module
selectively diagnoses said fault based on a change in oxygen of
exhaust gas measured after said EQR is transitioned to said lean
EQR.
11. A method comprising: generating a first signal a predetermined
period before an equivalence ratio (EQR) of an air/fuel mixture
supplied to an engine is transitioned from a non-lean EQR to a lean
EQR; and creating a reserve torque between when said first signal
is generated and when said EQR is transitioned to said lean
EQR.
12. The method of claim 11 further comprising: increasing at least
one engine airflow parameter before said EQR is transitioned to
said lean EQR; and retarding spark timing before said EQR is
transitioned to said lean EQR.
13. The method of claim 12 further comprising maintaining said at
least one engine airflow parameter until said EQR is transitioned
from said lean EQR to a second non-lean EQR.
14. The method of claim 13 further comprising: transitioning said
EQR from said non-lean EQR to a rich EQR during a first period,
wherein said non-lean EQR is a stoichiometric EQR; transitioning
said EQR from said rich EQR to said lean EQR during a second period
that is after said first period; increasing said at least one
engine airflow parameter before said first period; and maintaining
said at least one engine airflow parameter until said EQR is
transitioned from said lean EQR to said second non-lean EQR.
15. The method of claim 14 further comprising: retarding said spark
timing as said at least one engine airflow parameter increases; and
further retarding said spark timing as said EQR transitions from
said non-lean EQR to said rich EQR.
16. The method of claim 11 further comprising: generating a second
signal based on said lean EQR; and creating said reserve torque
based on said second signal.
17. The method of claim 11 further comprising transitioning said
EQR to said lean EQR after said reserve torque is created.
18. The method of claim 11 further comprising transitioning said
EQR to said lean EQR a predetermined period after said first signal
is generated.
19. The method of claim 11 further comprising selectively
diagnosing a fault in a catalyst associated with said engine after
said EQR is transitioned to said lean EQR.
20. The method of claim 19 further comprising selectively
diagnosing said fault based on a change in oxygen of exhaust gas
measured after said EQR is transitioned to said lean EQR.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Patent Application No. 61/039,524, filed on Mar. 26, 2008. The
disclosure of the above application is incorporated herein by
reference in its entirety.
FIELD
[0002] The present disclosure relates to internal combustion
engines and more particularly to torque compensation.
BACKGROUND
[0003] The background description provided herein is for the
purpose of generally presenting the context of the disclosure. Work
of the presently named inventors, to the extent it is described in
this background section, as well as aspects of the description that
may not otherwise qualify as prior art at the time of filing, are
neither expressly nor impliedly admitted as prior art against the
present disclosure.
[0004] Internal combustion engines combust an air and fuel mixture
within cylinders to drive pistons, which produces drive torque.
Airflow into the engine is regulated via a throttle. More
specifically, the throttle adjusts throttle area, which increases
or decreases air flow into the engine. As the throttle area
increases, the air flow into the engine increases. A fuel control
system adjusts the rate that fuel is injected to provide a desired
air/fuel mixture to the cylinders. Increasing the air and fuel to
the cylinders increases the torque output of the engine.
[0005] Engine control systems have been developed to control engine
torque output to achieve a desired torque. Traditional engine
control systems, however, do not control the engine torque output
as accurately as desired. Further, traditional engine control
systems do not provide as rapid of a response to control signals as
is desired or coordinate engine torque control among various
devices that affect engine torque output.
SUMMARY
[0006] A reserve torque system comprises a first module and a
reserve torque module. The first module generates a first signal a
predetermined period before an equivalence ratio (EQR) of an
air/fuel mixture supplied to an engine is transitioned from a
non-lean EQR to a lean EQR. The reserve torque module creates a
reserve torque between when the first signal is generated and when
the EQR is transitioned to the lean EQR.
[0007] In other features, the reserve torque system further
comprises an actuation module. The actuation module increases at
least one engine airflow parameter and retards spark timing before
the EQR is transitioned to the lean EQR.
[0008] In still other features, the actuation module maintains the
at least one engine airflow parameter until the EQR is transitioned
from the lean EQR to a second non-lean EQR.
[0009] In further features, the first module transitions the EQR
from the non-lean EQR to a rich EQR during a first period and
transitions the EQR from the rich EQR to the lean EQR during a
second period that is after the first period. The non-lean EQR is a
stoichiometric EQR. The actuation module increases the at least one
engine airflow parameter before the first period and maintains the
at least one engine airflow parameter until the EQR is transitioned
from the lean EQR to the second non-lean EQR.
[0010] In still further features, the actuation module retards the
spark timing when the at least one engine airflow parameter
increases and further retards the spark timing while the EQR
transitions from the non-lean EQR to the rich EQR.
[0011] In other features, the first module generates a second
signal based on the lean EQR and the reserve torque module creates
the reserve torque based on the second signal.
[0012] In still other features, the first module transitions the
EQR to the lean EQR after the reserve torque is created.
[0013] In further features, the first module transitions the EQR to
the lean EQR a predetermined period after the first signal is
generated.
[0014] In still further features, the first module selectively
diagnoses a fault in a catalyst associated with the engine after
the EQR is transitioned to the lean EQR.
[0015] In other features, the first module selectively diagnoses
the fault based on a change in oxygen of exhaust gas measured after
the EQR is transitioned to the lean EQR.
[0016] A method comprises generating a first signal a predetermined
period before an equivalence ratio (EQR) of an air/fuel mixture
supplied to an engine is transitioned from a non-lean EQR to a lean
EQR and creating a reserve torque between when the first signal is
generated and when the EQR is transitioned to the lean EQR.
[0017] In other features, the method further comprises increasing
at least one engine airflow parameter before the EQR is
transitioned to the lean EQR and retarding spark timing before the
EQR is transitioned to the lean EQR.
[0018] In still other features, the method further comprises
maintaining the at least one engine airflow parameter until the EQR
is transitioned from the lean EQR to a second non-lean EQR.
[0019] In further features, the method further comprises
transitioning the EQR from the non-lean EQR to a rich EQR during a
first period, wherein the non-lean EQR is a stoichiometric EQR;
transitioning the EQR from the rich EQR to the lean EQR during a
second period that is after the first period; increasing the at
least one engine airflow parameter before the first period; and
maintaining the at least one engine airflow parameter until the EQR
is transitioned from the lean EQR to the second non-lean EQR.
[0020] In still further features, the method further comprises
retarding the spark timing as the at least one engine airflow
parameter increases and further retarding the spark timing as the
EQR transitions from the non-lean EQR to the rich EQR.
[0021] In other features, the method further comprises generating a
second signal based on the lean EQR and creating the reserve torque
based on the second signal.
[0022] In still other features the method further comprises
transitioning the EQR to the lean EQR after the reserve torque is
created.
[0023] In further features, the method further comprises
transitioning the EQR to the lean EQR a predetermined period after
the first signal is generated.
[0024] In still further features, the method further comprises
selectively diagnosing a fault in a catalyst associated with the
engine after the EQR is transitioned to the lean EQR.
[0025] In other features, the method further comprises selectively
diagnosing the fault based on a change in oxygen of exhaust gas
measured after the EQR is transitioned to the lean EQR.
[0026] Further areas of applicability of the present disclosure
will become apparent from the detailed description provided
hereinafter. It should be understood that the detailed description
and specific examples are intended for purposes of illustration
only and are not intended to limit the scope of the disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] The present disclosure will become more fully understood
from the detailed description and the accompanying drawings,
wherein:
[0028] FIG. 1 is a functional block diagram of an exemplary engine
system according to the principles of the present disclosure;
[0029] FIG. 2 is a functional block diagram of an exemplary engine
control system according to the principles of the present
disclosure;
[0030] FIG. 3 is a functional block diagram of an exemplary reserve
torque system according to the principles of the present
disclosure;
[0031] FIG. 4 is a flow diagram depicting exemplary steps performed
by the reserve torque system according to the principles of the
present disclosure; and
[0032] FIGS. 5A-5E are exemplary illustrations of operations of
reserve torque systems according to the principles of the present
disclosure.
DETAILED DESCRIPTION
[0033] The following description is merely exemplary in nature and
is in no way intended to limit the disclosure, its application, or
uses. For purposes of clarity, the same reference numbers will be
used in the drawings to identify similar elements. As used herein,
the phrase at least one of A, B, and C should be construed to mean
a logical (A or B or C), using a non-exclusive logical or. It
should be understood that steps within a method may be executed in
different order without altering the principles of the present
disclosure.
[0034] As used herein, the term module refers to an Application
Specific Integrated Circuit (ASIC), an electronic circuit, a
processor (shared, dedicated, or group) and memory that execute one
or more software or firmware programs, a combinational logic
circuit, and/or other suitable components that provide the
described functionality.
[0035] An engine control module (ECM) controls an equivalence ratio
(EQR) of an air/fuel mixture combusted within an engine. For
example, the ECM may control the EQR based on a stoichiometric EQR
during normal engine operation. In some circumstances, however, the
ECM may receive a command to adjust the EQR to a lean EQR (i.e.,
EQR<stoichiometric EQR).
[0036] The ECM according to the present disclosure creates a
reserve torque before adjusting the EQR to the lean EQR. More
specifically, the ECM increases at least one engine airflow
parameter (e.g., throttle opening) and retards spark timing,
thereby creating a reserve torque. This reserve torque may be used
to smooth the torque output when the EQR is adjusted to the lean
EQR. Without the reserve torque, a sag (i.e., a decrease) in the
torque output may occur when the EQR is transitioned to the lean
EQR.
[0037] In some circumstances, the EQR may be transitioned to a rich
EQR (i.e., EQR>stoichiometric EQR) before or after the EQR is
transitioned to the lean EQR. In such circumstances, the ECM
according to the present disclosure may create the reserve torque
before the EQR is transitioned to the rich EQR. If the EQR is
transitioned from the lean EQR to the rich EQR, the increased
engine airflow parameters used to create the reserve torque are
maintained during the rich EQR while the spark timing is retarded.
This reserve torque may later be used to smooth the torque output
when the EQR is adjusted from the rich EQR to the stoichiometric
EQR. Without the reserve torque, a sag in the torque output may
also occur when the EQR is transitioned from the rich EQR to a
non-rich EQR (e.g., stoichiometric EQR).
[0038] Referring now to FIG. 1, a functional block diagram of an
engine system 100 is presented. The engine system 100 includes an
engine 102 that combusts an air/fuel mixture to produce drive
torque for a vehicle based on a driver input module 104. The engine
system 100 may be of a hybrid vehicle, such as a series-type hybrid
vehicle or a parallel-type hybrid vehicle. Air is drawn into an
intake manifold 110 through a throttle valve 112. An engine control
module (ECM) 114 commands a throttle actuator module 113 to
regulate opening of the throttle valve 112, thereby controlling
airflow into the intake manifold 110.
[0039] Air from the intake manifold 110 is drawn into a cylinder
116 through an associated intake valve 118. While the engine 102
may include multiple cylinders, for illustration purposes only, the
representative cylinder 116 is shown. For example only, the engine
102 may include 2, 3, 4, 5, 6, 8, 10, and/or 12 cylinders.
[0040] The ECM 114 also controls the amount of fuel injected by a
fuel injection system 120. For example, the fuel injection system
120 may inject fuel based on a signal from the ECM 114. The ECM 114
may adjust the amount of fuel injected by adjusting the length of
the signal (i.e., pulse width). In various implementations, the
fuel injection system 120 injects fuel into the intake manifold 110
at a central location. In other implementations, fuel may be
injected into the intake manifold 110 at multiple locations, such
as near the intake valve of each of the cylinders. Alternatively,
fuel may be injected directly into the cylinders.
[0041] The injected fuel mixes with the air and creates the
air/fuel mixture. A piston (not shown) within the cylinder 116
compresses the air/fuel mixture within the cylinder 116. A spark
actuator module 125 energizes a spark plug 128 associated with the
cylinder 116 based on a signal from the ECM 114. In this manner,
the ECM 114 controls the timing of the spark (i.e., spark
timing).
[0042] The spark timing may be specified relative to the time when
the piston is at its topmost position, referred to as to top dead
center (TDC), the point at which the air/fuel mixture is most
compressed. For example only, the spark timing may be set to a
minimum spark retard (relative to TDC) at which a maximum braking
torque is output. This spark timing is referred to as a maximum
braking torque (MBT) spark timing.
[0043] The combustion of the air/fuel mixture drives the piston
down (i.e., away from the TDC position), thereby driving a rotating
crankshaft (not shown). The piston then begins moving up again and
expels the byproducts of combustion through an associated exhaust
valve 122. The byproducts of combustion are exhausted from the
vehicle via an exhaust system 124.
[0044] The exhaust system 124 includes a catalytic converter 126
(CAT). The catalytic converter 126 includes one or more catalysts
that react with various components of the exhaust gas. Oxygen
sensors 127U and 127D measure concentration of oxygen in the
exhaust gas and are located upstream and downstream of the
catalytic converter 126, respectively.
[0045] An intake camshaft 129 may control opening of the intake
valve 118, while an exhaust camshaft 130 may control opening of the
exhaust valve 122. In various implementations, multiple intake
camshafts may control multiple intake valves per cylinder and/or
may control the intake valves of multiple banks of cylinders.
Similarly, multiple exhaust camshafts may control multiple exhaust
valves per cylinder and/or may control exhaust valves for multiple
banks of cylinders.
[0046] The time at which the intake valve 118 is opened may be
varied with respect to piston TDC by an intake cam phaser 131. The
time at which the exhaust valve 122 is opened may be varied with
respect to piston TDC by an exhaust cam phaser 132. A phaser
actuator module 134 controls the intake cam phaser 131 and the
exhaust cam phaser 132 based on signals from the ECM 114.
[0047] The engine system 100 may include a boost device that
provides pressurized air to the intake manifold 110. For example,
FIG. 1 depicts a turbocharger 140. Alternate engine systems may
include a supercharger (not shown) that provides compressed air to
the intake manifold 110 and is driven by the crankshaft.
[0048] The turbocharger 140 is powered by exhaust gases flowing
through the exhaust system 124, and provides a compressed air
charge to the intake manifold 110. The air used to produce the
compressed air charge may be taken from the intake manifold 110.
Compression of the air and/or heat radiated by the exhaust system
124 may heat the compressed air charge. An intercooler (not shown)
may also be included to decrease the temperature of the compressed
air charge.
[0049] A wastegate 142 may also be included to allow exhaust gas to
bypass the turbocharger 140, thereby reducing the output (or boost)
of the turbocharger 140. The ECM 114 controls the turbocharger 140
via a boost actuator module 144. The boost actuator module 144 may
modulate the boost of the turbocharger 140 by controlling the
position of the wastegate 142.
[0050] Various control mechanisms (i.e., actuators) of the engine
system 100 may vary respective engine parameters of the engine 102.
For example, the throttle actuator module 113 may change the
opening of the throttle valve 112 (i.e., an actuator position).
Similarly, the spark actuator module 125 may control an actuator
position that corresponds to spark timing.
[0051] Other control mechanisms that vary engine parameters
include, for example, the phaser actuator module 134, the boost
actuator module 144, and the fuel injection system 120. The term
actuator position with respect to these control mechanisms may
correspond to intake and exhaust cam phaser angles, boost pressure
and EGR valve opening, and amount of fuel injected,
respectively.
[0052] Various sensors may be used to measure various engine
parameters throughout the engine system 100. The ECM 114 may use
signals from the sensors to make control decisions for the engine
system 100 and/or adjust actuator positions. The sensors may
include an engine output speed (EOS) sensor 150, a manifold
absolute pressure (MAP) sensor 154, and/or a mass airflow (MAF)
sensor 156. Other sensors that are not shown in FIG. 1 may include,
for example, an engine coolant temperature (ECT) sensor, an oil
temperature sensor, an intake air temperature (IAT) sensor, and/or
any other suitable sensor.
[0053] The EOS sensor 150 measures the output speed of the engine
102 in revolutions per minute (rpm) based on rotation of the
crankshaft. The MAP sensor 154 measures the pressure within the
intake manifold 110. In various implementations, engine vacuum may
be measured, where engine vacuum is the difference between ambient
air pressure and the pressure within the intake manifold 110. The
MAF sensor 156 measures the mass flowrate of air into the engine
102. While the MAF sensor 156 is depicted as being located upstream
of the throttle valve 112, the MAF sensor 156 may be located in any
suitable location, such as in a common packaging with the throttle
valve 112.
[0054] Referring now to FIG. 2, a functional block diagram of an
exemplary engine control system 200 is presented. The ECM 114
includes an axle torque arbitration module 240 that arbitrates
between driver inputs from the driver input module 104 and other
axle torque requests. For example, driver inputs may include
accelerator pedal position. Axle torque requests may include torque
reduction requested during wheel slip by a traction control system
and/or torque requests to control speed from a cruise control
system.
[0055] Axle torque requests may also include requests from an
adaptive cruise control module, which may vary a torque request to
maintain a predetermined following distance. Axle torque requests
may also include torque increases due to negative wheel slip, such
as when a tire of the vehicle slips with respect to the road
surface while the torque produced by the engine 102 is
negative.
[0056] Axle torque requests may also include brake torque
management requests and torque requests intended to prevent vehicle
over-speed conditions. Brake torque management requests may reduce
engine torque to ensure that engine torque does not exceed the
ability of the brakes to hold the vehicle when the vehicle is
stopped. Axle torque requests may also be made by chassis stability
control systems.
[0057] The axle torque arbitration module 240 outputs a predicted
torque and an immediate torque. The predicted torque is the amount
of torque that will be required in the future to meet the driver
torque request and/or the driver's speed requests. The immediate
torque is the amount of torque required at the present moment to
meet temporary torque requests. The immediate torque may be
achieved using engine actuators that respond quickly, while slower
responding engine actuators may be targeted to achieve the
predicted torque.
[0058] For example, adjusting the spark timing, the amount of fuel
injected by the fuel injection system 120, the timing of fuel
injection, and/or cylinder deactivation may be accomplished in a
relatively short period of time. Accordingly, the spark timing, the
amount of fuel injected, and/or the fuel injection timing may be
adjusted to provide the immediate torque. Engine airflow actuators,
such as the cam phaser positions, the opening of the throttle valve
112, and boost may require a longer period of time to be adjusted
(relative to the fast actuators). Accordingly, the throttle
actuator module 113, the phaser actuator module 134, the boost
actuator module 144, and/or other engine airflow actuators may be
targeted to meet the predicted torque.
[0059] The propulsion torque arbitration module 242 arbitrates
between the predicted and immediate torque and propulsion torque
requests. Propulsion torque requests may include torque reductions
for engine over-speed protection, torque reductions during a gear
shift, and/or torque increases for stall prevention. Propulsion
torque requests may also include torque requests from a speed
control module, which may control the EOS during idle, limit the
EOS, and/or control the EOS during coastdown, such as when the
driver removes their foot from the accelerator pedal. Propulsion
torque requests may also include a clutch fuel cutoff, which may
reduce engine torque when the driver depresses the clutch pedal in
a manual transmission vehicle.
[0060] A reserves/loads module 244 selectively adjusts the
predicted torque request output by the propulsion torque
arbitration module 242 based on reserve torque requests. The
reserves/loads module 244 may also selectively adjust the immediate
torque request based on load requests. The reserves/loads module
244 outputs the predicted and immediate torque requests to an
actuator module 246.
[0061] The actuation module 246 generates actuator specific torque
requests based on the predicted and/or immediate torque requests.
More specifically, the actuation module 246 determines how the
predicted and immediate torque requests will be best achieved and
generates actuator specific torque requests accordingly.
[0062] For example, changing the throttle valve 112 allows for a
wide range of torque control. However, opening and closing the
throttle valve 112 is relatively slow. Disabling cylinders provides
for a wide range of torque control, but may produce drivability and
emissions concerns. Changing spark timing is relatively fast, but
does not provide much range of control. In addition, the amount of
control possible with spark (spark capacity) changes as the amount
of air entering the cylinder 116 changes.
[0063] The actuation module 246 generates an air torque request
that is transmitted to an air control module 248. The air control
module 248 determines desired actuator positions for the engine
airflow actuators based on the air torque request and generates
signals accordingly. For example, the air control module 248
determines a desired area, which corresponds to an opening of the
throttle valve 112 at which the air torque request may be produced.
The desired area is output to the throttle actuator module 113,
which adjusts the throttle valve 112 based on the desired area.
[0064] The air control module 248 may also determine a desired air
per cylinder (APC) based on the air torque request. The desired APC
corresponds to a volume of air within the cylinder 116 at which the
air torque request may be produced. A phaser scheduling module 250
determines desired intake and exhaust cam phaser positions based on
the desired APC. The phaser actuator module 134 then adjusts the
intake and exhaust cam phasers 131 and 132 to create the desired
intake and exhaust cam phaser positions.
[0065] The air control module 248 may also determine a desired MAP
based on the air torque request. The desired MAP corresponds to a
MAP at which the air torque request may be produced. The desired
MAP is output to a boost scheduling module 252 that controls the
boost actuator module 144 based on the desired MAP. The boost
actuator module 144 in turn controls the boost device, such as the
turbocharger 140 and/or a supercharger. The air control module 248
may also determine desired parameters for other engine airflow
actuators, such as an EGR system,
[0066] The air control module 248 may adjust the torque requests
for the engine airflow actuators based on an estimated air torque
of the engine 102. The estimated air torque may represent a maximum
amount of torque that the engine 102 is immediately capable of
producing under the current airflow conditions. The maximum amount
of torque may be achieved when the spark timing is set to a
calibrated spark timing.
[0067] A torque estimation module 254 uses the intake and exhaust
cam phaser positions along with the MAF signal to determine the
estimated air torque. In other implementations, the torque
estimation module 254 may use actual or measured phaser positions.
Further discussion of torque estimation can be found in commonly
assigned U.S. Pat. No. 6,704,638 entitled "Torque Estimator for
Engine RPM and Torque Control," the disclosure of which is
incorporated herein by reference in its entirety.
[0068] The actuation control module 248 generates torque requests
for fast actuators based on the immediate torque request. For
example, the actuation control module 248 outputs a spark torque
request to a spark control module 256. The spark control module 256
determines a desired spark timing (e.g., advance) based on the
spark torque request. The desired spark timing corresponds to a
spark timing at which the immediate torque request may be produced.
The spark actuator module 125 adjusts the spark timing based on the
desired spark timing. The actuation module 246 may also output
torque requests to other fast actuators, such as a cylinder
deactivation system (not shown).
[0069] A fuel/EQR control module 258 determines a desired fuel
amount and outputs the desired fuel amount to the fuel injection
system 120. The fuel injection system 120 injects the desired
amount of fuel. The desired fuel amount corresponds to an amount of
fuel to provide an air/fuel mixture having a desired equivalence
ratio (EQR) to the engine 102. For example, during normal engine
operation, the fuel/EQR control module 258 generally determines the
desired fuel amount to provide an air/fuel mixture having a
stoichiometric EQR (e.g., EQR of 1.0).
[0070] The EQR of a given air/fuel mixture corresponds to a ratio
of the respective masses of fuel and air of the air/fuel mixture in
relation to the masses of fuel and air of the stoichiometric
air/fuel mixture. For example only, the EQR of a given air/fuel
mixture may be determined using the equation:
E Q R = ( m fuel m O 2 ) ( m fuel m O 2 ) Stoich , ##EQU00001##
where m.sub.fuel is the mass of fuel, m.sub.O2 is the mass of air,
and Stoich is a stoichiometric air/fuel mixture.
[0071] Various vehicle systems may request production of a reserve
torque. Reserved torque may be used to smooth the torque output of
the engine 102 and/or the EOS when torque fluctuations (e.g., sags)
would otherwise occur. For example only, a catalyst light-off
system may request a reserve torque to perform catalyst light-off.
The reserves/loads module 244 selectively adjusts the predicted
torque requests based on reserve torques requested to allow for
realization of the reserved torque as needed.
[0072] Various vehicle systems may also request torque for a load
that is applied to the engine 102. For example, a power steering
pump (not shown) assists a driver in steering the vehicle. In
assisting the driver, however, the power steering pump applies a
load to and draws torque from the engine 102. Accordingly, a load
request may be made to compensate for the load applied by the power
steering pump. The reserves/loads module 244 may selectively
increase the immediate torque request based on load requests.
[0073] One or more vehicle systems may command changes in the
air/fuel mixture, for example, to perform a diagnostic. For
example, a catalyst diagnostic module 260 requests a change in the
air/fuel mixture. More specifically, the catalyst diagnostic module
260 commands a change in the EQR. In various implementations, the
catalyst diagnostic module 260 transitions the EQR from the
stoichiometric EQR to a rich EQR (i.e., EQR>stoichiometric EQR),
from the rich EQR to a lean EQR, and from the lean EQR back to the
stoichiometric EQR. In other implementations, the catalyst
diagnostic module 260 transitions the EQR first to the lean EQR and
later to the rich EQR.
[0074] The catalyst diagnostic module 260 commands the EQR changes
to determine the oxygen storage capacity of the catalytic converter
126 and to determine whether the catalytic converter 126 is faulty.
Faults may be determined based on the oxygen concentration
measurements (OSU and OSD) provided by the upstream and downstream
oxygen sensors 127U and 127D, respectively. Further discussion of
the operation of the catalyst diagnostic can be found in commonly
assigned U.S. Pat. application Ser. No. 11/145,284, filed Jun. 3,
2005, the disclosure of which is expressly incorporated herein by
reference in its entirety.
[0075] Referring now to FIG. 3, a functional block diagram of an
exemplary reserve torque system 300 is presented. The
reserves/loads module 244 according to the present disclosure
creates a reserve torque before a lean EQR command is executed.
While the principles of the present disclosure will be discussed as
they relate to a lean EQR command from the catalyst diagnostic
module 260, the principles of the present application are also
applicable other commands to adjust the EQR to a lean EQR.
[0076] The reserves/loads module 244 includes a predicted torque
module 302, an immediate torque module 304, and a reserve torque
module 306. The reserves/loads module 244 may also include a timer
(not shown). The predicted and immediate torque modules 302 and 304
receive the predicted and immediate torque requests, respectively,
from the propulsion torque arbitration module 242.
[0077] The predicted torque module 302 outputs the predicted torque
request based on the predicted torque request from the propulsion
torque arbitration module 242. Likewise, the immediate torque
module 304 outputs the immediate torque request based on the
immediate torque request from the propulsion torque arbitration
module 242. The immediate torque module 304 may selectively adjust
the immediate torque request based on load requests.
[0078] The reserve torque module 306 selectively instructs the
predicted torque module 302 to adjust (e.g., increase) the
predicted torque request based on reserve torque requests. Reserve
torque requests may include, for example, a reserve request for
idling, traction control, and/or transmission related reserve
torque requests. Other reserve torque requests may include a
reserve torque request for engaging of the air conditioning
compressor clutch, for engaging of a generator (e.g., alternator or
belt alternator starter), to warm a catalyst of the exhaust system
124, and/or to purge air trapped within a fuel system.
[0079] The reserve torque module 306 determines a desired reserve
torque based on the reserve torque requests. For example only, the
desired reserve torque may be determined based on one of the
reserve torque request having the largest magnitude. Alternatively,
the desired reserve torque may be determined as a sum of one or
more of the reserve torque requests.
[0080] The reserve torque module 306 outputs the desired reserve
torque to the predicted torque module 302. The predicted torque
module 302 determines and outputs the predicted torque request to
create the desired reserve torque. More specifically, the predicted
torque module 302 increases the predicted torque request based on
the desired reserve torque. For example only, the predicted torque
module 302 may sum the desired reserve torque and the predicted
torque request from the propulsion torque arbitration module
242.
[0081] The predicted torque module 302 outputs the predicted torque
request to the actuation module 246, which controls the air torque
request based on the predicted torque request. Accordingly, the
actuation module 246 increases the air torque request when the
reserve torque is requested. The air control module 248 then
increases one or more engine airflow parameter (e.g., throttle
opening) based on the increased air torque request. The maximum
amount of torque that the engine 102 could produce (i.e., the
estimated air torque) also increases under the increased engine
airflow conditions.
[0082] To offset the increase in the estimated air torque, the
actuation module 246 decreases the spark torque request, which
causes the spark control module 256 to adjust the spark timing.
More specifically, the spark control module 256 retards the spark
timing. In this manner, the spark timing is adjusted to offset the
increase in torque output that would otherwise occur under the
increased engine airflow conditions. Retarding the spark timing
reserves torque, which can be rapidly realized by advancing the
spark timing.
[0083] As stated above, the catalyst diagnostic module 260 requests
a reserve torque to perform a diagnostic regarding reliability of
one or more of the catalysts within the catalytic converter 126.
The catalyst diagnostic module 260 may perform this diagnostic at a
predetermined time, such as while the engine 102 is idling. For
example only, the diagnostic, and therefore the reserve torque, may
be requested a predetermined period after the engine 102 is
started. The diagnostic may be performed by adjusting the EQR in a
predetermined sequence, such as from a lean EQR to a rich EQR, or
from a rich EQR to a lean EQR. However, adjusting the EQR from a
non-lean EQR to a lean EQR causes a sag (i.e., decrease) in torque
output by the engine 102.
[0084] The catalyst diagnostic module 260 generates an enable
signal (i.e., Cat Enable) before the catalyst diagnostic is
performed. More specifically, the catalyst diagnostic module 260
generates the enable signal before the EQR is transitioned to the
lean EQR. The catalyst diagnostic module 260 also generates an EQR
signal (i.e., EQR.sub.CAT) that corresponds to the lean EQR that
the EQR will be transitioned to. The enable signal and the EQR
signal are provided to the reserve torque module 306.
[0085] The reserve torque module 306 according to the present
disclosure determines the desired reserve torque for the lean EQR
when the enable signal is generated. For example only, the desired
reserve torque for the lean EQR may be determined based on the lean
EQR that the EQR will be transitioned to. In various
implementations, the desired reserve torque may be determined based
on a lookup table of desired reserve torques indexed by EQR. For
example only, the desired reserve torque may increase as the lean
EQR requested becomes more lean.
[0086] The reserve torque module 306 outputs the desired reserve
torque for the lean EQR to the predicted torque module 302, which
adjusts the predicted torque request based on the desired reserve
torque. In this manner, the reserve torque module 306 increases at
least one engine airflow parameter to create the reserve torque for
the lean EQR.
[0087] Assuming that the immediate torque request is steady-state,
the actuation module 246 decreases the spark torque request, which
causes retarding of the spark timing. Retarding the spark timing
offsets the increase in torque output that would otherwise be
experienced due to the increase engine airflow parameters. The EQR
is maintained at the stoichiometric EQR while the engine airflow
parameters are increasing.
[0088] When the reserve torque for the lean EQR has been created,
the reserve torque module 306 allows the EQR to be transitioned.
For example only, the catalyst diagnostic module 260 may assume
that the reserve torque has been created a predetermined period
after the increased predicted torque request was generated. The
predetermined period may be determined based on, for example, the
magnitude of the reserve torque, the change in the predicted torque
request, the change in the air torque request, the lean EQR, and/or
the change in the engine airflow parameters necessary to effectuate
the reserve torque.
[0089] The catalyst diagnostic module 260 adjusts the EQR via the
fuel/EQR control module 258. More specifically, the fuel/EQR
control module 258 adjusts the EQR based on the EQR.sub.CAT when
commanded by the catalyst diagnostic module 260. When the fuel/EQR
control module 258 adjusts the EQR based on the EQR commanded by
the catalyst diagnostic module 260, the fuel/EQR control module 258
may transmit an EQR signal to the air control module 248 that
corresponds to the commanded EQR. The air control module 248 may
use the EQR signal ensuring that the commanded EQR is achieved.
[0090] The fuel/EQR control module 258 may also transmit a source
signal to the air control module 248 when the catalyst diagnostic
module 260 commands the EQR transitions. The source signal
indicates that the catalyst diagnostic module 260 is then
controlling the EQR. The air control module 248 may thereafter
ignore any changes in the air torque request until control of the
EQR returns to normal operation.
[0091] Referring now to FIG. 4, a method 400 depicting exemplary
steps performed by the ECM 114 is presented. One or more of the
steps of the method 400 may be combined or performed simultaneously
without altering the principles of the present disclosure. The
method 400 may be performed in one or more different modules of the
ECM 114.
[0092] Control begins in step 402 where control determines whether
a lean EQR request is present. If true, control continues to step
404; otherwise, control remains in step 402. For example only, a
lean EQR request is a request to change the EQR to a lean EQR
(e.g., an EQR<stoichiometric EQR). The lean EQR request may be
from, for example, the catalyst diagnostic module 260. The EQR may
also be transitioned to a rich EQR before being transitioned to the
lean EQR.
[0093] In step 404, control determines a reserve torque based on
the lean EQR requested. Control also commands the creation of the
reserve torque in step 404. Control continues in step 406 where
control adjusts one or more engine airflow parameters and the spark
timing to create the reserve torque for the lean EQR requested.
More specifically, control increases the engine airflow parameters
and retards the spark timing to create the reserve torque. The
engine airflow parameters adjusted may include throttle opening
area, opening of the intake and/or exhaust valves 118 and 122, the
boost device, and/or other engine airflow parameters.
[0094] Control continues in step 408 where control determines
whether the reserve torque has been created. If true, control
proceeds to step 410; otherwise, control returns to step 406. For
example only, control may determine that the reserve torque has
been created after a predetermined period of time passes after the
creation of the reserve torque is commanded. Alternatively, control
may determine that the reserve torque has been created when the
difference between the immediate torque and the estimated torque is
approximately equal to the reserve torque.
[0095] In step 410, control adjusts the EQR to the lean EQR
requested. In some circumstances, such as in the case of the
catalyst diagnostic module 260, control may adjust the EQR to a
rich EQR before the transition to the lean EQR. In this manner,
control adjusts the EQR to the lean EQR after the reserve torque
has been created. In other words, control creates the reserve
torque for the lean EQR before the EQR is adjusted to the lean EQR.
The reserve torque can then be rapidly utilized to smooth the
torque output of the engine 102 and/or the EOS. Control continues
in step 412 where control determines whether the lean EQR request
is complete. If true, control proceeds to step 414; otherwise,
control returns to step 410 and maintains the lean EQR.
[0096] In step 414, control returns to normal operation and adjusts
the EQR based on the stoichiometric EQR. Control then ends. In this
manner, the engine airflow parameters remain unchanged while the
EQR controlled at a non-stoichiometric EQR. Constant engine airflow
parameters may be desirable depending on the reason for the lean
EQR request.
[0097] For example only, constant engine airflow parameters may aid
the catalyst diagnostic, as a change in airflow may incorrectly
cause a diagnosis of a fault in the catalytic converter 126 that
may be attributable to the change in airflow. While FIG. 4 shows
control ending after step 414, control may return to step 402 and
repeat the steps of FIG. 4 continuously during operation of the
engine 102 when a lean EQR request is generated.
[0098] Referring now to FIGS. 5A-5E, exemplary illustrations of
various approaches employed by reserve torque systems are
presented. Exemplary trace 502 tracks the EQR of the air/fuel
mixture supplied to the engine 102 for combustion. Exemplary trace
504 tracks the state of the enable signal for a lean EQR request,
such as the enable signal from the catalyst diagnostic module
260.
[0099] Exemplary trace 506 tracks the estimated air torque of the
engine 102. The estimated air torque 506 corresponds to a maximum
amount of torque that the engine 102 is capable of producing under
the current engine airflow conditions. Exemplary trace 508 tracks
the air torque request. The estimated air torque 506 generally lags
behind the air torque request 508 due to a delay that is
attributable to the period necessary for air to be ingested into
the engine 102 (i.e., the cylinders). Exemplary trace 510 tracks a
base (e.g., idle) spark timing and exemplary trace 512 tracks the
spark timing.
[0100] In various implementations, a reserve torque may have
already been created when an EQR change to a lean EQR is commanded.
For example, an idle reserve torque is likely present during times
when the catalyst diagnostic is performed. The base spark timing
510 represents the spark timing to accommodate preexisting reserve
torques, such as the idle reserve torque. The spark timing 512 may
also be retarded from the MBT timing to the base spark timing 510,
for example, to prevent knocking.
[0101] Referring to FIG. 5A, the lean EQR request 504 is generated
before time 520, indicating an upcoming transition to a lean EQR.
The desired reserve torque is determined and the air torque request
508 is increased. The estimated air torque 506 increases as the
engine airflow parameters increase based on the air torque request
508. The spark timing 512 is retarded while the estimated air
torque 506 increases.
[0102] In some instances, another EQR change may be commanded
before the EQR 502 is transitioned to the lean EQR command is
executed. For example, in FIG. 5A, the EQR 502 is commanded to a
rich EQR (i.e., EQR>stoichiometric EQR) before the lean EQR
command is executed. The EQR 502 is transitioned to the rich EQR
starting at time 520, the time at which the estimated air torque
506 reaches the air torque request 508.
[0103] As the estimated air torque 506 increases, the rich EQR
supplied to the engine 102 after time 520 would cause an increase
in torque output. The spark timing 512, however, is further
retarded to offset the increase in torque output that would
otherwise occur. In this manner, the desired reserve torque is
created before the EQR is transitioned to the lean EQR. An
additional reserve torque (a fuel reserve torque) is created by the
excess fuel supplied to create the rich EQR.
[0104] Between times 522 and 524, the EQR 502 is transitioned from
the rich EQR to the lean EQR. The reserved torque can be utilized
to smooth the torque output, which would otherwise decrease. In
other words, the spark timing 512 is advanced to increase and
smooth the torque output as the EQR transitions toward the lean
EQR. The air torque request 508 is maintained during the
transition. In this manner, the engine airflow parameters remain
unchanged during the transition.
[0105] Starting at time 526, the EQR 502 is transitioned back to
the stoichiometric EQR (i.e., EQR approximately 1.0). The air
torque request 508 is decreased, the estimated air torque 506
decreases, and the spark timing 512 is retarded. The EQR 502
reaches the stoichiometric EQR at time 528, while the estimated air
torque 506 is decreasing toward the air torque request 508. The
spark timing 512 is advanced to offset the decrease in torque
output that would otherwise occur due to the decreasing engine
airflow parameters. The approach illustrated in FIG. 5A may require
a significant retard of the spark timing and may decrease fuel
economy. However, engine airflow parameters are maintained during
the EQR 502 transitions.
[0106] Referring to FIG. 5B, the EQR 502 is again commanded to the
rich EQR before the lean EQR command is executed. In FIG. 5B,
however, the air torque request 508 is not increased while the rich
EQR is supplied to the engine 102. Instead, the amount of fuel
supplied is increased, thereby creating the rich EQR. The spark
timing 512 is retarded as the EQR 502 transitions to the rich EQR,
thereby creating a reserve torque (a fuel reserve torque).
[0107] At time 532, the lean EQR request 504 is generated,
signaling an upcoming EQR transition to a lean EQR. Accordingly,
the air torque request 508 is increased to create the reserve
torque for the lean EQR. The estimated air torque 506 increases as
the engine airflow parameters increase based on the air torque
request 508. Between times 532 and 534, the spark timing 512 is
advanced, utilizing the reserved torque created by the rich
EQR.
[0108] The EQR 502 begins transitioning to the lean EQR after time
534 and the spark timing 512 is further advanced to offset the
decrease in torque output that may otherwise occur due to the lean
EQR. After time 536, when the torque output stabilizes, the spark
timing 512 may then be retuned to the base (e.g., idle) spark
timing 510.
[0109] The approach illustrated in FIG. 5B may require the spark
timing 512 to be advanced beyond the base spark timing 510. Such an
advance may affect the system for which the base spark timing 510
was employed. Additionally, the engine airflow parameters are
changing (increasing) while the EQR 502 is lean. However,
maintaining the engine airflow parameters while the EQR 502 is rich
may increase fuel economy.
[0110] Referring now to FIG. 5C, the EQR 502 is again commanded to
the rich EQR before the lean EQR request 504 is executed. Before
time 540, the EQR 502 transitions to the rich EQR. To offset the
increase in torque output that would otherwise occur, the spark
timing 512 is retarded as the EQR 502 increases, thereby creating a
reserve torque (a fuel reserve torque). The air torque request 508,
however, is maintained while the EQR is rich.
[0111] The lean EQR request 504 is enabled at time 542, and the air
torque request 508 is increased. The engine airflow parameters and
the estimated air torque 506 accordingly increase toward the air
torque request 508. As the engine airflow parameters increase, the
spark timing 512 is retarded, thereby increasing the reserve
torque. In this manner, the reserve torque for the lean EQR is
created before the EQR is transitioned to the lean EQR.
[0112] The estimated air torque 506 reaches the air torque request
508 at time 546. The EQR 502 is transitioned to the lean EQR
beginning at time 546. As the EQR 502 transitions to the lean EQR,
the spark timing 512 is advanced until time 548 when the EQR 502
reaches the lean EQR.
[0113] The approach illustrated in FIG. 5C may increase fuel
economy as the air torque request 508 and the engine airflow
parameters are maintained before time 542. Additionally, the engine
airflow parameters are maintained while the EQR 502 is lean. The
time when the EQR 502 is commanded to the lean EQR, however, may
need to be delayed for the creation of the reserve torque.
[0114] Unlike FIGS. 5A-5C, in FIG. 5D, the EQR 502 may be commanded
to the lean EQR before being commanded to the rich EQR. The lean
EQR request 504 is enabled at time 550, and the air torque request
508 is increased. The estimated air torque 506 accordingly
increases, and the spark timing 512 is retarded to offset the
increase in torque output that would otherwise occur. This
retardation of the spark timing 512 coupled with the increased
engine airflow parameters creates the reserve torque for the lean
EQR.
[0115] At time 552, the time when the estimated air torque 506
reaches the air torque request 508, the EQR 502 is transitioned to
the lean EQR. At this time, the spark timing 512 is advanced to
increase the torque output and offset the decrease that would occur
due to the lean EQR transition. The air torque request 508 and the
spark timing 512 are maintained until time 554 when the EQR 502
transitions from the lean EQR. At time 554, the EQR 502 is
transitioned to the rich EQR. The air torque request 508 is
decreased and the spark timing 512 is adjusted as the engine
airflow parameters decrease to smooth torque output.
[0116] Referring now to FIG. 5E, like FIG. 5D, the lean EQR is
commanded before the EQR 502 is transitioned to the rich EQR.
Before time 560, the lean EQR request 504 is enabled. The air
torque request 508 is increased. The estimated air torque 506
increases accordingly and the spark timing 512 is retarded, thereby
creating the reserve torque for the upcoming lean EQR.
[0117] Starting at time 560, the EQR 502 is transitioned to the
lean EQR. During the transition, the reserved torque is utilized to
offset the torque output sag that would otherwise occur. More
specifically, the spark timing 512 is advanced, which offsets the
torque output decrease that would otherwise be attributable to the
lean EQR. The air torque request 508 is maintained throughout a
later EQR transition to the rich EQR, which begins at time 562. The
spark timing 512 is retarded as the EQR 502 transitions to the rich
EQR to offset the increase in torque output that would otherwise
occur.
[0118] Those skilled in the art can now appreciate from the
foregoing description that the broad teachings of the disclosure
can be implemented in a variety of forms. Therefore, while this
disclosure includes particular examples, the true scope of the
disclosure should not be so limited since other modifications will
become apparent to the skilled practitioner upon a study of the
drawings, the specification, and the following claims.
* * * * *